The present invention relates to a high voltage circuit breaker, particularly a blast-piston breaker.
In high-voltage installations with a rated voltage of, for example, more than 100 kV, compressed-gas circuit breakers are used, as is well known, which are generally blast-piston ("puffer") breakers, or may also operate according to the two-pressure system. A fluorine-containing electronegative gas, particularly sulfurhexafluroide (SF6), is used as both the compressed gas and the insulating gas. The electrodes are hollow and have nozzle-like ends through which the switching gases are removed, and are mutually oppositely disposed. At least the part of the electrode adjoining its respective end is made of carbon, particularly graphite. The inside diameters of the nozzle-like ends and the spacing between the nozzle-like ends of the two electrodes are chosen so that good quenching action on an arc which is drawn when the breaker opens is obtained.
In breakers in which the nozzle-like ends of the two electrodes are arranged opposite each other spaced by a fixed distance, the arc is drawn by a movable bridging contact which in general is disposed at the outer cylindrical surface of the nozzle-like ends of the electrodes. The arc can be drawn further by a contact within the nozzle-like ends or by providing movable nozzle-like ends which are separated from each other by an axial distance for interrupting the current. By substantially radially outwardly directing the gas flow, the base of the arc is blown into the mouths of the nozzle-like ends. In high-voltage breakers, for example having a rated voltage of 245 kV and more, several such interrupter units of high breaking capacity can be connected in series.
It is known that the switching gap must be cleared and kept free of charge carriers after a quenching operation. Heretofore this was accomplished by blasting the arc by means of special coaxial contacts movable from within the nozzle-like ends of the electrode into the space between the nozzle-like ends. The individual nozzle-like electrode ends of the interrupter unit were shaped at their mutually opposite end faces so that a minimum distance was obtained between the electrodes to provide the required dielectric strength in the cold condition. The passage openings of the breaker contacts could be configured to prevent the arc from passing to the nozzle-like ends.
According to DE-AS 10 55 643, the end faces of the nozzle-like ends were shaped so that they formed a surface of revolution, the generatrix of which is a circular arc. In a two electrode system in which the nozzle-like end faces oppose each other at a fixed distance, the end faces of the electrodes were shaped such that the main cylindrical portion of the electrodes had a curvature greater than that of the nozzle-like ends, as disclosed in DE-AS 22 20 897, in order to guide the flow of the gas stream radially to the axis of rotation of the system.